The design of the Escorial perfectly reflects the role of Philip II as the leading monarch of the Catholic Reformation. In the 16th century other European rulers construct buildings of great secular splendour. Philip's creation, of no less splendour, is as much monastery as palace.

At the centre of the complex is a large church surmounted by a dome (like its contemporary, St Peter's in Rome). The buildings to the north of the church are the monastery. A matching range to the south is the king's palace. Here Philip, when in residence, has his office. Here he ploughs painstakingly through mountains of paperwork, much of it bringing to his notice the seemingly insoluble problem of the Netherlands.

William of Orange and the duke of Alba: 1559-1568

Philip II's first regent in the Netherlands is his half sister, Margaret of Parma. There is local unrest under her rule, but also an assumption that compromise may be possible. William of Orange, heir to large estates in the Netherlands and known from his quiet skill in negotiation as William the Silent, emerges as one of the leaders of those demanding change.

Religious toleration and freedom from the attentions of the Inquisition are among the demands most commonly made. But the Protestant cause is not well served by the intemperate behaviour of some of the Calvinists. Iconoclastic mobs go on the rampage in August 1566, smashing the treasures of many churches in the Netherlands.

Hearing of such events, Philip II resolves upon severe measures. He instructs the duke of Alba, a veteran of many campaigns, to march north with an army from Italy. He is to restore order in the Netherlands regardless of what measures may be required.

Alba, arriving in August 1567, introduces a rule of terror but does so at first by stealth. He lulls two of the leading dissident nobles, the counts of Egmont and of Horn, into accepting his hospitality. He then has them arrested, summarily tried and executed. They are merely the most distinguished victims of Alba's tribunal, which becomes known in the Netherlands as the Council of Blood.

Alba's agents act with the quiet efficiency of a modern police state. In 1568, in the early hours of Ash Wednesday (the morning after the pre-Lent carnival, when revellers are likely to be off their guard), fifteen hundred suspects are visited in their homes and taken from their beds. All, according to Alba's note on the incident, are executed.

William of Orange, wisely keeping his distance from Alba, slips into exile - and so remains available to lead the armed resistance to Spanish rule which now begins to develop.

Spanish access to the Netherlands: 1568-1588

Unrest in the Netherlands gives urgency to another strand of Philip II's foreign policy. The duke of Alba's journey to take up his appointment in Brussels has been a roundabout one through Philip's continental possessions - by sea from Spain to northern Italy, before marching an army through the Alps and up through Burgundy, Lorraine and Luxemburg.

An easier way to the Netherlands, round the obstacle of hostile France, is the sea route up the Atlantic coast. But this requires at least neutrality on the English side of the Channel, a waterway too narrow to be risked if there are enemies on both shores.

This practical consideration reinforces Philip's pious wish to see the Catholic religion restored to England. From 1580 Spanish support is secretly given to Jesuit missionaries infiltrating English Catholic society.

Equally any Englishman inclined to rebellion on behalf of the Catholic claimant to the throne, Mary Queen of Scots, can be sure of practical Spanish assistance as soon as there is a realistic chance of success. For these and other reasons, relations between Spain and England deteriorate from the late 1560s and become rapidly worse during the 1580s.

Spain and England: 1568-1588

During the years when Philip II plots secretly against Elizabeth, a more public clash of interests is steadily pushing Spain into a position of open hostility. After Elizabeth's appropriation of Spanish gold on its way to the Netherlands in 1568, relations between Spain and England are formally severed for five years. By 1585 Elizabeth is actively supporting the Dutch rebels in the Netherlands. She sends 6000 men to their aid in that year under the earl of Leicester.

Meanwhile English incursions into the rich Spanish territories of Latin America have been escalating since the pioneering efforts of John Hawkins.

The main English voyages of plunder have been carried out by Francis Drake, a relative of Hawkins. Sailing from Plymouth to the Caribbean in May 1572 with just two small ships and seventy-three men, he spends more than a year depriving the Spanish of their precious metals, taking gold and silver from captured ships, from treasure houses on land and even from intercepted mule trains.

During his voyage round the world, in 1577-80, Drake goes one better - surprising the Spanish on the previously safe Pacific coast, where in 1579 he captures a fat, defenceless vessel, the Cacafuego, carrying 26 tons of silver, 80 lb. of gold and 13 chests of money. (The captain of a Spanish ship later provides an interesting glimpse of life On board the Golden Hind.)

So far these adventures have had the quality of piracy. But Drake's departure from Plymouth for the Caribbean in 1585, with a fleet of about thirty ships, looks much more like an expedition of war. He and his men spend several months plundering Spanish settlements, burning houses, sinking ships, destroying whatever they cannot profitably remove.

Coinciding with Elizabeth's despatch of troops to the Netherlands in the same year, this provocation finally persuades Philip that he must invade England. His pious wish to bring his first wife's country back to Roman Catholicism coincides now with the need to protect his territories.

Even so, he has to suffer one more affront. While Philip assembles his fleet in Cadiz in 1587, Drake sails into the crowded harbour and burns or sinks some thirty ships (an impertinence which becomes known in England as 'singeing the king of Spain's beard'). Much of the fleet being assembled consists of galleys, the standard Spanish warship of the time.

Drake's ability to manoeuvre at Cadiz affects the forthcoming expedition, because it convinces Philip that he must use sailing ships. By May 1588 he has assembled a fleet of galleons.

Spanish Armada: 1588

The encounter between the Spanish Armada and the English fleet in the Channel in August 1588 is the first of a new kind of naval battle, and one in which the English tactics suggest the way forward.

The Spanish have been accustomed to fighting at sea with galleys, as at Lepanto only seventeen years previously. A galley imposes a certain pattern on a battle. Guns can only point forward from the bow, where the main weapon, the ram, is also located. Assault consists in rowing straight at the enemy. Once at close quarters the ideal is to sink the enemy ship, with the ram. Next best is to grapple it and swarm aboard for hand-to-hand combat - in a technique going back to the Roman navy and the 'raven'.

The Armada (or in full Flota Armada Invencible, Armed Invincible Fleet) is the first Spanish war fleet to consist of sailing vessels, but its composition implies the use of galley tactics. The Spanish galleons are heavy; their guns fire large cannon balls, devastating at close quarters but of limited range; and the sailors on board the warships are more than twice outnumbered by soldiers, valueless in a sea battle unless ships come alongside.

The English fleet, consisting of smaller and swifter vessels, is armed with cannon which fire a lighter ball over a greater range. And the ships are almost entirely manned by trained seamen, with only a handful of soldiers.

Compared to later grand battles at sea, the fight with the Armada is strung-out and scrappy. The English, under the command of Lord Howard of Effingham, attack off Plymouth on July 31, off Portland Bill on August 2 and off the isle of Wight on August 4. Their light cannon reach the Spanish ships but do little damage. The fleet safely reaches Calais, where the plan is to pick up an army from the Netherlands and to ferry it across the Channel against England. But the army has not arrived.

During the night of August 7 the English send fire ships in among the anchored fleet, causing the Spanish to cut their cables in disarray. The next day the only real engagement takes place, off Gravelines.

The Spanish run out of cannon shot first, whereupon the English sail in close enough to do serious damage. At least three ships are sunk and a great many more severely battered before the English too run out of shot. The Armada escapes into the North Sea. The Spanish commander, the duke of Medina Sidonia, cannot now return through the Channel. He attempts to take his shattered fleet round the north of Scotland and into the Atlantic.

Ships founder or are wrecked on Scottish and Irish coasts. Of the 130 vessels which sailed from Corunna in June, only 67 limp back to Spain. The English, with a very much easier return voyage to their home ports, lose not a single ship.